The quantity and diversity of information available from public government sources is now quite large. Most people associate governmental information exclusively with prescriptive information such as laws and regulations. However, governments, especially local ones, are using the Web to provide a number of services that are mainly informative and aim at improving the quality of life of citizens and at promoting the local community, for example job placement services, tourist information, and so forth. Finally, government e-services available to citizens represent one of the most frequent and critical points of contact between public administrations and citizens. In addition to common services such as ID cards and permits, e-services represent the only practical way of providing incentives and support to specific classes of citizens.
Key Terms in this Chapter
User Focus: The set of documents corresponding to a user-defined composition of concepts; initially, the entire knowledge base.
Taxonomy, reduced: In a dynamic taxonomy, a taxonomy, describing the current user focus set F, which is derived from the original taxonomy by pruning from it all the concepts not related to F.
Extensional Inference Rule: Two concepts A and B are related if there is at least one item d in the knowledge base which is classified at the same time under A (or under one of A’s descendants) and under B (or under one of B’s descendants).
Facet: One of several top level (most general) concepts in a multidimensional taxonomy. In general, facets are independent and define a set of “orthogonal” conceptual coordinates.
Subsumption: A subsumes B if the set denoted by B is a subset of the set denoted by A (B ? A)
Extension, deep: Of a concept C, denotes the shallow extension of C union the deep extension of C’s sons.
Zoom: A user interface operation, that defines a new user focus by OR’ing user-selected concepts and AND’ing them with the previous focus; a reduced taxonomy is then computed and shown to the user.
Extension, shallow: Of a concept C, denotes the set of documents classified directly under C.
Taxonomy, multidimensional: A taxonomy where an item can be classified under several concepts
Taxonomy, one-dimensional: A taxonomy where an item can be classified under a single concept only
Taxonomy: A hierarchical organization of concepts going from the most general (topmost) to the most specific concepts. A taxonomy supports abstraction and models subsumption (IS-A and/or PART-OF) relations between a concept and its father. Tree taxonomies can be extended to support multiple inheritances (i.e., a concept having several fathers).